Time to Total Hip Arthroplasty Among Patients in the US Military Health System.

Importance: Total hip arthroplasty (THA) delays can be deleterious. Robust evaluation of time to THA enables data-driven improvement efforts across the US Military Health System. Objective: To evaluate time to THA after hip osteoarthritis diagnosis by patient-, care-, and structural-level factors. Design, Setting, and Participants: This retrospective cohort study evaluated medical records from US military and civilian health care facilities from March 1, 2015, to June 21, 2024. Participants were adult TRICARE enrollees diagnosed with hip osteoarthritis between March 1, 2018, and March 30, 2023, without diagnosis in the past 3 years, who received at least 1 additional visit 1 week to 3 years after the index date. Data were analyzed from July 2024 to August 2025. Main Outcomes and Measures: Time to THA within 3 years of index diagnosis. Results: Of 37 239 patients diagnosed with hip osteoarthritis (median [IQR] age, 59 [50-64] years; 21 553 [58%] male; 320 American Indian and Alaska Native [1%]; 1603 Asian and Pacific Islander [4%]; 8123 Black [22%]; 2041 Hispanic [5%]; 23 327 White [63%]; 1825 another race and ethnicity [5%]), 10 502 (28%) received a THA within 3 years. A piecewise exponential additive model indicated incidence rate ratios (IRRs) for time to THA were lower for Asian and Pacific Islander (IRR, 0.76; 95% CI, 0.66-0.88), Black (IRR, 0.79; 95% CI, 0.74-0.85), and Hispanic (IRR, 0.84, 0.73-0.96) patients compared with White patients; patients with psychiatric (IRR, 0.79; 95% CI, 0.76-0.83), pain-related (IRR, 0.69; 95% CI, 0.66-0.72), or obesity (IRR, 0.92; 95% CI, 0.88-0.96) diagnoses before the index diagnosis; patients with elevated comorbidity index scores (IRR, 0.85; 95% CI, 0.74-0.97); those diagnosed in the purchased care system (IRR, 0.38; 95% CI, 0.36-0.40) and in later years (IRR, 0.97; 95% CI, 0.95-0.99); and patients with 1 (IRR, 0.83; 95% CI, 0.77-0.90) or more (IRR, 0.75; 95% CI, 0.70-0.81) injections or 2 or more imaging visit days (IRR, 0.77; 95% CI, 0.69-0.86) before the index diagnosis. Retired service members (IRR, 1.39; 95% CI, 1.24-1.56) and family members (IRR, 1.48; 95% CI, 1.30-1.69) had higher incidence of THA compared with active-duty service members. Male patients had higher incidence compared with female patients (IRR, 1.20; 95% CI, 1.11-1.31). Patients with increasing orthopedic surgeon visit days (IRR, 1.67; 95% CI, 1.64-1.69), opioid prescriptions (IRR, 1.02; 95% CI, 1.01-1.03), and imaging visit days (IRR, 1.26; 95% CI, 1.24-1.28) after the index diagnosis were also more likely to undergo THA. Variation across geographic areas was mixed. Conclusions and Relevance: In this cohort study of TRICARE enrollees, variation in THA receipt was identified across multilevel factors. These finding suggest that policy and programming decisions could benefit from including TRICARE-participating orthopedic surgeon locations, structural factors, and reimbursement models to optimize THA access.